Character generation system



FRANKLIN c. cHlANG 3,103,658

CHARACTER GENERATION SYSTEM Sept. 1963 4 Sheets-Sheet 1 Filed Jan. 13,1958 lllljlll-lu sept. 1o, 1963 Filed Jan. 13, 1958 FRANKLIN c. cl-uANG3,103,658

CHARACTER GENERATION SYSTEM 4 Sheets-Sheet 2 /i /i MH "f www ,/52 /g/AZQ L T J, o

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CHARACTER GENERATION SYSTEM Filed Jan. 1s, 195s 4 sheets-sheet s Flai?v50/ ANON /2/3/j ..../d if w /Z y Z//j 2 t 22425K... con ooo o n z 4 glio o o o 0 e o o o o o o o 0 o /Z @l /331/ o o o o n a i33 o 0 o o o o oo c @I il o o o o o o I o c o o V o o o 0 /Zl c Z2/f o o o o o n o `1943 o n o s @i o o o o o 0 MMA/MMM irrafA/ir/.s

Sept 10, 1963 FRANKLIN c. cHlANG 3,103,658

CHARACTER GENERATION SYSTEM 4 Sheets-Sheet 4 Filed Jan. 15, 1958inve/vir.;

United States Patent O 3,103,658 CHARACTER GENERA'HON SYSTEM Franklin C.Chiang, Palo Alto, Calif., assigner to International Business MachinesCorporation, New Yorlr, N .Y., a corporation of New York Filed Jan. 13,1958, Ser. No. 708,556 2 Claims. (Cl. 340-324) This invention relates toelectrical signalling, and more particularly to a system of charactergeneration for graphically reproducing and displaying selectedcharacters responsive to electric signals representing said characters.

The principal object of this invention is to provide a system forgeneration and displaying selected characters in ia signal-responsivedevice such as a cathode-ray tube from fa remote point by transmitting arelatively small number of electric pulses.

It is a further object of this invention to provide a plurality oicharacter-identification generators such that each generator permanentlyidentities a particular character and only a single signal isrequired to.trigger the generation of a selected character to be graphicallyreproduced. Also, depending upon the individual requirements of thecharacter reproductions, each character can be generated for a timeinterval as short as 25 microseconds, `or as long as many seconds, andcan be repeated as many times as desired to aid visual perception.

-Another object of this invention is to provide a system of charactergeneration wherein, in the case of long distance transmission, only oneidentification code is required for each character.

The above and other objects may be attained by employing this inventionwhich provides among its features a system in which a selected characteris reproduced graphically upon the repetitively scanned screen of acathode-ray tube by means of a pulse train generated in time relationwith the raster of the cathode-nay tube. Diiferent pulse trains forreproducing the different characters are generated by means of aplurality of character-generators-a separate character generator beingprovided for each character that is to be graphically reproduced. 'Ilhesystem also includes means for selecting any desired one of thecharacter generators, and means ior connecting the selectedcharacter-generator to the cathode-ray tube.

Other objects `and advantages will become apparent from a considerationof the following detailed description :taken -in conjunction with the'accompanying drawings, wherein:

FIG. 1 is a schematic circuit diagram of an exemplary embodiment of thisinvention, ia plurality of charactergenerators being shown thereinrepresented by blocks 1011 through 109;

FIG. 2 is a schematic circuit diagram of a typical charcoter-generator10A;

FIG. 3 is a schematic view showing the construction of a delay lineemployed in character-generator 10A;

FIG. 4 is a representation of several of the characters which may bereproduced and displayed; and

FIG. 5 is a schematic circuit diagram of another exemplary embodiment.

The embodiment illustrated in FIG. 1 comprises a plurality ofcharacter-generators A through 10', connected in parallel with eachgenerator identifying a particular Character, such las a letter of thealphabet or a numeral. The subscript identities the character which thatgenerator reproduce. As is best shown in FIGS. 2 and 3, eachcharacter-generator (10A for example) includes a delay line 111 and aplurality of pick-up units 121 through 127 in axially spaced relation toeach other along the delay ence numerals 1321 through 1325; etc.Selected windings of each unit are connected in parallel withcorresponding windings of other units and to respective output lines 151through 1155 to provide a pulse train which gencrate a selectedcharacter, as hereinafter explained. In the generator 10A shown in FIG.2, the windings are interconnected so as to define a matrix coded togenerate the character A. Isolation resistors 14 are connected in serieswith the respective windings to prevent undesirable interactionstherebetween.

In the specific embodiments herein illustrated and described, dellectioncircuitsof the cathode-ray tubes I19 and i19 are arranged to Yprovide `ascanning raster composed of live approximately vertical scanning lines.In other words, horizontal sweep generator 21 operates with a periodlive times as long as that of the vertical sweep generator 231. Each ofdelay lines 11 has a delay time equal `to the scanning time of onevertical line of the raster of the cathode-ray tube. Approximately atthe beginning of eadh vertical scanning line an electric pulse issupplied by a pulse generator 219 through lines 11 to the input end ofeach delay line 11 of the character generators. As each such pulsetravels down a delay line 11, voltage pulses are induced rst in the livewindings of pick-up unit 121, then in the ve windings of pick-up unit122, etc., so that seven sets of live pulses each are successivelyproduced within each character-generator during each vertical scanningline. In a manner hereinafter explained, each of the five output lines151 through `1511 of a selected character-generator is connected insuccession to the cathode-ray tube 1-9 during each scanning frame offive lines, so that pulses from thirty live windings may be transmittedto the cathode-ray tube at the thirty live different points in thescanning cycle, respectively. 'Ilhe delay line 11 is terminated with aresistor 16 equal to the characteristic impedance of theline to preventreflections from the lower end of the line.

As will be noticed in FIG. 3, the seven pick-up units 121 through 127are annular and extend around delay line 11. Each pick-up unit may beadjusted in position along the length of line 11 to adjust the timing ofthe pulses induced in its windings. may be of conventional construction;la helix -or the like of insulated wires wound about an insulating form1-7 and one or more metal foil grounding strips 18. This constructionprovides a fairly large distributed inductance or capacitance, wherebyappreciable time delays (e.g., up to several hundred microseconds) arereadily obtained. y

The thirty ve windings 11311 through 137i,- are arranged as shown inFIG. 2, to define a rectangular matrix in which corresponding windingsott' the seven units represent seven horizontal rows of the matrix andthe ve windings of each unit represent live vertical columns of thematrix. Each intersection of a matrix row with a matrix columnrepresents a point on the screen of the cathode-ray tube. lf the coil atsuch `an intersection is connected into a circuit, a visible spot willbe generated at the corresponding point on the screen, by meanshereinafter described. l-Ience, to obtain a coded interconnection of thewindings to identify a specific character, selected windings ineach'ventical matrix column are connected in-parallel, so that whensuccessive electric pulses are transmitted down the delay line 11, andthe ve columns of the matrix are connected in succession to thecathode-ray tube, a pulse train is supplied to the control electrode ofthe cathode-nay tube in timed relation with The delay line proper 3 thescanning raster to cause a graphic reproduction of the character definedby the coded matrix ofthe selected character generator.

The conventional cathode-ray tube 19 has an electron gun at the base ofthe neck, including a cathode 24 and a control electrode 25, to producea beam fof electrons which is acted upon by horizontal and verticaldeflection means 20 and 22 to produce a scanning raster upon the screen26. A raster may be defined as a pre-determined pattern of scanninglinesIwhich provide substantial uniform coverage of an area. An electricalcircuit 13 inciudes horizontal and vertical sweep-generators 21 and 23which are connected to the deflection means 20 and 22 respectively ofthe cathode-ray tube 19. Each of the two sweep generators produces asawtooth waveform scanning signal `for deflecting the electron beam ofthe cathode-ray tube repetitively back and fort-h and up and down lthescreen 26. The period of the horizontal sweep generator is five times aslong as the period of vertical sweep generator 23, so that, in thiscase, the scanning lines are approximately vertical and there are live-vertical lines in each scanning frame.

Electric circuit 18 also includes a pulse generator `29. Pulse generator29 and vertical sweep generator 23 are synchronized by any suitablemeans (ifor example, by using the pulses generated by generator 29 assynchronizing pulses fior generator 23) so that generator 29 supplies apulse to each input line 11' of the character generators approximatelyat the beginning of each vertical scanning line. Horizontal sweepgen-erator 21 is synchronized with another pulse generator 30 whichsupplies a pulse substantially concurrently with each fifth pulsesupplied by generator 29.

The cathode-ray tube 19 is biased to cut-off by any suitable means, suchas the positive voltage supply 27 connected to the cathode 24.Therefore, no light appears at the screen 26` except at points in thescanning cycle when pulses are supplied to the control grid 25. rIihus,each pulse supplied to grid 25 produces a visible spot on screen 26, ata point in the screen that depends upon the timing of the pulse relativeto the scanning cycle. It is evident that any desired character can bedisplayed on the screen 26 by supplying a properly timed train of pulsesto grid 2S during each scanning cycle. Accelerating voltage ror theelectron beam of the cathoderay tubeis provided by a voltage supply 28.

Means are provided for selectively connecting one of the character'generators to the cathode-ray tube and in this instance comprises aselector switch 31 having a plurality of input leads 321 through 325adapted toi be connected 4to the output leads 151 through 155 of aselected character generator. Switch 31 may be manually or automaticallyoperated, and in practice may be a highspeed electronic orelectromagnetic switching network responsive to coded signals receivedfrom an electrical communications system, or the dike. However, thespecic construction of the switch is of no concern to this invention.yFor present purposes, switch 31 can be considered to be a simple,manually operated, mechanical contact, electrical switch.

Assume that the input leads 321 to 325 have been connected to the outputleads 151 through 155 respectively of the character generator A, whichhas been coded to have a matrix identifying the character A. ,It beobserved that leads 321 through 325 are connected to respective ones ofthe iive normally-closed or non-conductive :gates 331 through 335. Thus,each pulse appears at one of the output leads 151` through 155 .for theselected character generator and passes through switch 31 to arespective one of the .gates 331 through 335.

Each of the gates is connected by an output lead 34 into the controlelectrode 25 of the cathode-ray tube 119. 'Ilhese gates are Well-knowncircuits that transmit electric pulses from an input lead to an outputlead only when the gate is opened, or made conductive, by voltagessupplied to anotherinput lead.`

ln this case, the gates 331 through 335 have their second or controlinput leads connected to respective taps 351 through 355 of a masterdelay line 36. Thus, an electric pulse traveling yfrom lett to rightalong delay line 36 will open each of the gates 331 through 335 insuccession. Delay line 36 is terminated by resistor 31 equal to thecharacteristic impedance of the line, to prevent undesirable reectionsfrom the right end of the delay line.

`Pulse `generator 30 provides a pulse approximately at the begin-ning ofeach scanning frame. 'l'ihese pulses are amplified by an amplifier 38,and are supplied to the left end of the master delay line 36. Theduration of each pulse so supplied to line 36 is made approximatelyequal to the lduration of one vertical scanning line, which is oneiifthof the duration of the scanning frame. Therefore, Agate 331 is openduring the scanning time of the first vertical line of each frame. It isclosed during the scanning of the other `four lines of each frame.

Delay lli-ne 36 -is constructed to provide between each of its taps andthe next tap a ltime delay approximately .equal to the time intervalbetween vertical scanning lines. Thus, :gate 332 is open during thesecond vertical scanning rline of each frame, gate 333 is open dur-ingthe third vertical lline of each frame, etc.

Considering the period of the pulses provided by the generator 29 to beTn, then the second pulse generator 30 and the circuit 18 is arrangedso` as to provide to the master delay line 36 pulses having a period of5Tn, and a duration of Tn. Thus, as each of the pulses supplied to themaster delay line 36 travels from one end to the other en'd thereof,each of the gates 331 through 335 in succession is opened for a timeinterval Tn. Since the total delay of lines 11 in the charactergenerator is Tn, the complete train of pulses appears in each of thelines 151 through 155 during each interval Tn. Therefore, each gate insuccession transmits a complete train of pulses yfrom one output line ofthe `selected character generator to control grid 25 of the cathode-raytube. This permits a complete sequence of the pulses received from theselected character generator output leads 151 through 155 to passsequentially into the leads 34. In turn, the control electrode 25 of thecathode-ray tube gun is driven more positive by each pulse allowing theelectron beam to pass through the deiiection means 20, 22 and produceIupon the cathode-ray tube 19 a pattern of dots thus forming thecharacter selected for display. Thus, the matrix connecti'ons of theselected character generator are displayed on a screen 26, to provide agraphical display of lthe se- `lected character. When switch 31 isconnected to generator 10A, a pattern of dots Iforms the characterA onscreen 26. i

Considering once again the character generator 10A representative of thecharacter A (FIG. 2), it .will be seen that the matrix is so arrangedthat if the` generator y29 drives the delay line 11 by imparting atrain` of pulses thereto, one such pulse is` supplied to the upper endof line 11 approximately at the beginning orf each vertical scanningIli-ne. During the tirst scanning line ot the frame, line 151 isconnected to cathode-ray tube 19 through open gate 331, while theremaining lines 152` through 155flead to closed gates. Hence,considering only the tirst matrix, from the iirst scanning line at atime T1, the windings 1371 and 13-15 of the tirst pick-up unit 121 willreceive a pulse which is transmitted through switch 31 and gate 331 tothe control electrode v25 of the cathode-ray tube, Similarly, at time T2the windings 1351 and 1355 of the unit 122 receive a pulse; at time T2the windings 1351 and 1355 of the unit 123 receive a pulse; at time T1the windings 1311 through 13.15 of the units `121 each receive a pulse;while at a time T5 and T5 windings 1332through 1331 and 1322 through132,l respectively each receive a pulse; and at a time T., windings 1312and 1315 and 1314 each receive a pulse. All of the pulses aresequentially transmitted through -output leads 151 through 155 as apulse trainand then through respective gates 331 through 1 5 t 335 tothe contnol electrode 25 by action of the delay li-ne 36.

In the manner hereinbefore indicated, these pulses'will be I.transmittedthrough switch 31" to respective ones of the gates 331 through 335 whichwill be actuated sequentially'to produce these pulses in the samesequenceupon the control electrode 25 of the cathode-ray tube to -reectthe sequence prearranged and coded into the matrix of the selectedcharacter generator. At the Sametime, since rangement and function issimilar to 4the embodiment of FIGS. 1-4, except for the arrangement ofthe means whereby the train of pulses from a selected charactergenerator 19'), through 109 is selectively switched intro connectionwith the electric circuit 18 and the cathode-ray tube 19. The selectorswitch 31', similar to the selector switch 31, is now connected intolead 4l) from pulse generator 29 so that a Iselected character generatorcan be connected through its input line 11. On each :of the output lines151 through 155 of each character generator, there is provided diodes421 through 425 respectively to prevent feedback through charactergenerators other than die one selectively connected into switch 31.

Corresponding output lines of each character generator 16A through 199are connected into respective common lines 441 through 445, which are inturn connected to delay line 36, through respective leads 461 through465, at spaced locations therealong. Thus, for instance, line 441connects all of the output leads 151 of character generators A-1il5 tothe right end of master delay line 36 (as viewed in FIG. 5).Corresponding leads 152, '5 and 154 of the other generators areconnected into delay line 36 at selected points intermediate its ends lwhile all of the output'leads, corresponding to 155 of charactergenerator IWA, connect into delay line 36 at its left end as viewed inFIG. 5 Delay line 36 acts to sequentially store the pulses transmittedthereto by the output leads 151 through 155 and deliver these pulsessequentially at its right end, as viewed in FIG. 5. The train of pulsesappearing at lthe right end of delay line A36 Will be supplied to thegrid 25' of cathode-ray t-ube 19' to function in t-he same manner asdescribed in connection with the embodiment of FIGS. 1-4. The horizontaland vertical sweep generators 21 and 23 are, in the form of theinvention of FIG. 5, connected into electromagnetic deflection means 48and 50 (in place of the electrostatic deflection means 20, 212 of FIGS.1 4) respectively acting upon the electron beam of the cathoderay tube19 to produce a scanning raster on the screen 26 of the tube.

Sweep generators 21 and `23 are synchronized, by suitable means, withthe pulses delivered by generator 29 to the character generators IWA`through 10's. As previously indicated, 4horizontal sweep generator 21operates with a period live times as long as that of the vertical sweepgenerator. Therefore, the pulse train of a selected character generator,such as 10A, will be fed into the master delay line 36 in sequence,stored in the delay line by being sequentially transmitted thereto, andappear sequentially at the control electrode 25 of the cathoderay tubefrom the end of master delay line 36', thus the character represented bythe selected pulse train will be graphically reproduced on the screen ofthe cathode-ray ytube in the same manner as explained in connection withthe embodiment of FIGS. 1 4.

Essentially then, the modification of FIG. 5 eliminates (l) the need fora switch for each one of the output leads on each character generator,(2)' the requirement for a plurality of gates in connection with themeans for selectively connecting a character generator to the cathoderaytube, and (3) the necessity for a separate pulse generator and a gatingamplifier `in its electrical circuit 18 'connecting the charactergenerators to the sweep generators of the cathode-ray tube, whencompared to the embodiment of the character generation system of FIGS. 14.

iFrom the foregoing, it will be seen that a desired character dened by acharacter generator may be selectively switched into the system and begraphically portrayed by actuation from an external source, which sourcemay be remote from the system, by employing in each character generatora plurality of pick-up units having separate windings which areinterconnected in a prearranged manner defining a matrix, and said coilsbeing excited by a delay line to produce a pulse or signal traincorresponding to the matrix selectively switchedv by means 31 or k31into connection, through a master delay line, in timed relation with theraster of a cathode-ray tube upon the screen of which the characterdelined by the matrix will be visually displayed, the horizontal andvertical sweep generators being synchronized with the pulse or signaltrain generated in a selected character generator.

Although the present illustration shows the coils arranged in rows inthe matrix and the cor-responding windings of the coils connected torepresent columns of the matrix, this relationship of rows and columnscan be reversed without departing from the concept of the invention byemploying conventional techniques well known to those skilled in theart. Also the delay lines 11 employed in the character generators may beprovided with taps in place of the inductively coupled pick-up units andas such would be similar in construction t0 delay lines 36 and 36.

It will be understood that this invention is not limited to specificembodiments herein illustrated and described, and that the followingclaims are intended to cover all changes and modications which fallwithin the true spirit and scope of the invention.

What is claimed is:

1. A system of character generation, comprising in combination, acathode-ray tube and deilection means therefor producing a scanningraster, a plurality of chairacter generators, each of said generatorsincluding a delay line and a plurality of coils spaced axially alongsaid delay line, each of said coils having a plurality of separatewindings thereon, said windings being interconnected to dene a matrixrepresenting a selected character with certain corresponding windings ofsaid coils being connected in parallel representing alinement of thematrix in a first direction and the windings on each coil itselfrepresenting alinement of the matrix in a second direction, an outputlead for each of said corresponding windings so that when said delayline is excited a sequential signal train can be applied to thecathode-ray tube in timed relation with the raster thereof, an electriccircuit synchronously connected to said cathode-ray tube deection meansfor driving the deflection means and connected to said plurality ofcharacter generators to drive said delay line in timed relation to saidraster, and rneans for selectively connecting one of said charactergenerators to said circuit and to said cathode-ray tube in response to areceived signal froman external actuation source, said means beingconnected to the control electrode of said cathode-ray tube andsynchronized with said electrical circuit whereby said sequential signaltrain will allow a beam of electrons to strike the screen of thecathode-ray tube under the control of said deflection means and producea raster in timed relation with said circuit whereby the characterdetermined by the matrix of the selected character generator will beVisually reproduced.

2. The combination according to claim 1 wherein said means comprises aswitch selectively connectable to said output leads, a plurality ofgates arrangedv in sequence and connected to said switch and to thecontrol electrode of the cathode-ray tube to -be thus connectedsequentially to said output leads, and a master delay line synchronouslyconnected to said circuit and to said gates to have the gates functionsequentially -in response to the sequential Isignal train transmittedfrom the matrix of the selected character generator through said outputleads and said gate, whereby the control electrode of said cathode-raytube will be driven in response to said signal train.

UNITED STATES PATENTS' Gloess Sept. 19, 1950 Wheeler Feb. 6, 1951 BakerMay `15, `1951 Baker June 12, 195,1 Eckert Jr. ..-i Aug. 10, 1954 ToulonOct. ,5,` 1954 Sheftelman Oct. 9, 1956 Young Mar.5, 1957 McNaney et al.June 24,` `1958 Gordon et al. Jan. 5, 1960 Triest Mar, 29, 1960

1. A SYSTEM OF CHARACTER GENERATION, COMPRISING IN COMBINATION, ACATHODE-RAY TUBE AND DEFLECTION MEANS THEREFOR PRODUCING A SCANNINGRASTER, A PLURALITY OF CHARACTER GENERATORS, EACH OF SAID GENERATORSINCLUDING A DELAY LINE AND A PLURALITY OF COILS SPACED AXIALLY ALONGSAID DELAY LINE, EACH OF SAID COILS HAVING A PLURALITY OF SEPARATEWINDINGS THEREON, SAID WINDINGS BEING INTERCONNECTED TO DEFINE A MATRIXREPRESENTING A SELECTED CHARACTER WITH CERTAIN CORRESPONDING WINDINGS OFSAID COILS BEING CONNECTED IN PARALLEL REPRESENTING ALINEMENT OF THEMATRIX IN A FIRST DIRECTION AND THE WINDINGS ON EACH COIL ITSELFREPRESENTING ALINEMENT OF THE MATRIX IN A SECOND DIRECTION, AN OUTPUTLEAD FOR EACH OF SAID CORRESPONDING WINDINGS SO THAT WHEN SAID DELAYLINE IS EXCITED A SEQUENTIAL SIGNAL TRAIN CAN BE APPLIED TO THECATHODE-RAY TUBE IN TIMED RELATION WITH THE RASTER THEREOF, AN ELECTRICCIRCUIT SYNCHRONOUSLY CONNECTED TO SAID CATHODE-RAY TUBE DEFLECTIONMEANS FOR DRIVING THE DEFLECTION MEANS AND CONNECTED TO SAID PLURALITYOF CHARACTER GENERATORS TO DRIVE SAID DELAY LINE IN TIMED RELATION TOSAID RASTER, AND MEANS FOR SELECTIVELY CONNECTING ONE OF SAID CHARACTERGENERATORS TO SAID CIRCUIT AND TO SAID CATHODE-RAY TUBE IN RESPONSE TO ARECEIVED SIGNAL FROM AN EXTERNAL ACTUATION SOURCE, SAID MEANS BEINGCONNECTED TO THE CONTROL ELECTRODE OF SAID CATHODE-RAY TUBE ANDSYNCHRONIZED WITH SAID ELECTRICAL CIRCUIT WHEREBY SAID SEQUENTIAL SIGNALTRAIN WILL ALLOW A BEAM OF ELECTRONS TO STRIKE THE SCREEN OF THECATHODE-RAY TUBE UNDER THE CONTROL OF SAID DEFLECTION MEANS AND PRODUCEA RASTER IN TIMED RELATION WITH SAID CIRCUIT WHEREBY THE CHARACTERDETERMINED BY THE MATRIX OF THE SELECTED CHARACTER GENERATOR WILL BEVISUALLY REPRODUCED.